Craig Smith had two goals and an assist, and Calle Jarnkrok had a goal and two assists for Nashville (16-12-5), which has won back-to-back games to start a four-game road trip. Pekka Rinne made 27 saves.
"It feels good," said Smith, who scored his first goal in 17 games. "That being said, I think a lot of games I'm right there in the right spots. I haven't changed much; I'm just trying to get into those pockets and find the lanes to be able to shoot. I was able to get a good look tonight."
[WATCH: All Predators vs. Islanders highlights]
Thomas Greiss allowed five goals on 15 shots and was pulled after the second period for New York (22-8-2), which had won eight straight at Nassau Coliseum and was 12-0-1 during the streak.
The Islanders held a 3-1 lead; they were 19-0-1 this season when scoring at least three goals and 57-2-3 since Barry Trotz took over as coach prior to last season (including shootout winners).
"We couldn't get a stop," Trotz said. "Our goalies have bailed us out so many times this year. We couldn't bail them out."
Video: NSH@NYI: Smith roofs shot in tight for second goal
Casey Cizikas scored shorthanded on a 2-on-1 to give New York a 3-1 lead at 8:11 of the second period, but Filip Forsberg started the Predators rally with a power-play goal 27 seconds later to make it 3-2 at 8:38.
Smith's second goal of the game tied it 3-3 when he was left alone at the edge of the left circle at 10:58.
"His work ethic has been really good," Nashville coach Peter Laviolette said of Smith. "It's nice that he gets rewarded with a night like tonight, scoring some big goals for us at the right time."
Nick Bonino gave the Predators a 4-3 lead on a redirection of Mattias Ekholm's shot from the point at 18:24.
Video: NSH@NYI: Bonino deflects Ekholm's shot past Greiss
Rocco Grimaldi made it 5-3 with 47 seconds left in the period with a shot from a sharp angle that squeaked past Greiss at the right post.
It was the first time the Islanders allowed four goals in a period since a 6-2 home loss to the Dallas Stars at Barclays Center on Nov. 18, 2018.
"This doesn't happen to us very often," Cizikas said. "It's definitely tough, but tomorrow's a new day. Wake up, come to the rink, do our work and get ready for the next one."
Jarnkrok scored on Nashville's first shot of the third period to make it 6-3 at 8:59. Roman Josi's power-play goal made it 7-3 at 11:36, and Ryan Johansen scored on a wraparound at 14:08 for the 8-3 final.
Video: NSH@NYI: Johansen, Jarnkrok combine for pretty goal
Semyon Varlamov made six saves in the third.
"You learn a lesson when you let up eight, that's for sure," Islanders captain Anders Lee said.
Smith gave Nashville a 1-0 lead at 4:39 of the first period.
Brock Nelson tied it at 2:55 of the second on an odd-man rush to make it 1-1, and Derick Brassard's power-play goal gave New York a 2-1 lead at 4:43.
"That was a huge win for us, especially going down 3-1 on a back-to-back in their building," Grimaldi said. "The response that we had on our power play after getting a [shorthanded goal] scored on them  seconds later and answer to make it 3-2, that was huge.
"Great response at the end of the second there, and obviously in the third, we just stuck to our game plan. I know in the past, we've kind of sat back on our heels and sometimes they start coming at us. But I thought today, we just kept going."
Video: NSH@NYI: Nelson rips wrister past Rinne on 2-on-1
They said it
"It's a yearlong battle; there's definitely things that can be lost on a road trip, that's for sure. You head out for whatever it is, five days, seven days, eight games, there's things that can go wrong, and you can certainly lose ground and take steps in the wrong direction. We can move up the standings and continue to climb, and I think the games in hand are really important, but there will be a lot of hockey left after Christmas." -- Predators coach Peter Laviolette
"It doesn't feel right, it doesn't feel like us. We put this behind us and move on. It's a long year. We're going to have a stinker. This [stinks], but it's over now. We've got to be better." -- Islanders captain Anders Lee
Need to know
Seven players (Smith, Forsberg, Bonino, Ekholm, Johansen, Jarnkrok, Ryan Ellis) had a multipoint game for the Predators, who scored six goals at even strength. … The eight goals were a season high for Nashville and the most New York has allowed under Trotz. The Islanders last allowed eight in an 8-4 loss to the Carolina Hurricanes at Barclays Center on March 13, 2017. … New York defenseman Nick Leddy had two shots and was minus-2 in 19:31 of ice time in his return after missing three games because of a lower-body injury. … Nashville won 5-2 at the New York Rangers on Monday.
Predators: At the Ottawa Senators on Thursday (7:30 p.m. ET; ESPN+, RDS2, TSN5, FS-TN, NHL.TV)
Islanders: At the Boston Bruins on Thursday (7 p.m. ET; NBCSN, SNE, SNO, SNP, TVAS, NESN, NHL.TV)
Video: Predators erupt for eight goals in rout of Islanders